1. Technical Field
This disclosure relates to circuits for generating pulse-width modulation (“PWM”) signals, including PWM signals that have an independently adjustable duty cycle and frequency.
2. Description of Related Art
PWM circuits may be built around a periodic sawtooth or triangular signal. The sawtooth or triangular signal may be compared against a constant control signal. The result may be a periodic pulse having a duty cycle that is dependent upon the level of the constant control signal. The frequency of the signal may also be changed to cause a corresponding change in the frequency of the PWM signal.
Circuits of this type, however, may be limited in the minimum pulse width which the circuit can controllably and stably generate. This may be due to propagation delays in the circuit and other factors. Changes in the frequency of the analog sawtooth or triangular signal can also affect its wave shape. This may cause corresponding changes in the duty cycle of the PWM signal, even though the level of the constant control signal does not change.